Several methods have been developed over the last decades to attach organic mono-layers on semi-conductors surfaces. Silicon has been the most widely investigated: especially, stable and densely packed mono-layers were obtained from alkenes and alkynes on hydrogen-terminated surfaces through the use of thermal conditions and photochemical reactions with UV or visible light. Stable and densely packed mono-layers are formed with these methods, opening applications in molecular electronics and sensors.
Since silicon carbide possesses properties intermediate to silicon (composition, energy band gap), mono-layer formation is possible on silicon carbide surfaces similar to silicon surfaces. Silicon carbide has been pursued for high power, high voltage applications, membrane purposes and for sensing in harsh environments.
Silicon-rich silicon nitride (SixN4) is also an interesting substrate regarding the formation of organic mono-layers, as it is widely used as insulator for microelectronics and microsystem coatings. Films of this material inhibit diffusion of water, oxygen, and sodium ions, and are widely used as a passivation layer in integrated circuits. Its popularity is mainly motivated by its superior physical and chemical inertness, as it provides an excellent alternative to silicon dioxide in microelectronic and membrane applications.
Polyethylene oxide modifications of surfaces have been used to provide protein repellent ability to those surfaces. For example, US 2005255514, incorporated by reference herein, discloses substrates such as silicon, glass, silica, quartz and metal oxide which are functionalised with a silane having an oligoethylene oxide group to provide protein-resistance.
U.S. Pat. No. 6,358,613, incorporated by reference herein, discloses a method for forming a covalently bound mono-layer on silicon surfaces comprising contacting a silicon substrate with an alkene or alkyne in the presence of a solvent-soluble Lewis acid.
U.S. Pat. No. 6,569,979, incorporated by reference herein, points in detail to the relevance of surfaces that are suitable for immobilization of biologically active materials such as RNA, DNA and fragments or derivatives thereof. U.S. Pat. No. 6,569,979 further discloses a method for modifying a non-oxidized silicon (001) surface, wherein functionalized 1-alkenes, in the absence of any intervening oxygen atoms, are reacted with hydrogen-terminated silicon under UV initiation. However, the method provides modified surfaces having a poor hydrophobicity as appears from the relatively low water contact angles. Modification by using tert.-butoxycarbonyl protected 10-amino-1-decene afforded a modified non-oxidized silicon (001) surface having a water contact angle θ of only 78.1°, i.e. near-identical to the value of non-modified hydrogen-terminated Si(001).
WO 02/19407, incorporated by reference herein, also discloses a method for covalently binding a functionalised alkene to a surface comprising hydrogen terminated silicon or hydrogen terminated germanium.
WO 02/66162, incorporated by reference herein, discloses a method for functionalising hydrogen terminated silicon surfaces with functionalised alkynes.
Korean patent application KR 2003/0054809, incorporated by reference herein, discloses a method for functionalising of hydrogen terminated silicon with w-amino alkenes in the presence of a radical initiator such as AIBN (azobisisobutyronitril) by irradiation with UV or by heating at 20°-150° C.
US 2004/213910, incorporated by reference herein, discloses a method for functionalising hydrogen terminated silicon surfaces with ω-(ethylene glycol oligomer)-alkenes by irradiation with UV.
US 2006/0134656, incorporated by reference herein, discloses a method for functionalising of hydrogen terminated silicon or carbon surfaces with ω-(ethylene glycol oligomer)-alkenes by irradiation with UV.
WO 2005/001461, incorporated by reference herein, also discloses a method for functionalising hydrogen terminated silicon surfaces with alkenes or alkynes.
WO 2005123273, incorporated by reference herein, discloses functionalized silicon and/or germanium surfaces, methods for the preparation of such functionalized silicon and/or germanium surfaces, the use of such functionalized silicon and/or germanium surfaces for the preparation of surface-bonded organic materials and the use thereof in industrial devices. The silicon and/or germanium surfaces comprise silicon nitride and silicon carbide, germanium nitride and germanium carbide, and silicon germanium surfaces.
WO 2007048924, incorporated by reference herein, discloses a method for grafting molecules of interest on a silicon substrate via a spacer compound, said grafting including at least one click chemistry reaction to the supports thus obtained as well as their uses in nanotechnologies and nanobiotechnologies, such as molecular electronics, the manufacture of biochips or of sensors.
Consequently, the prior art discloses methods for functionalising hydrogen terminated silicon, germanium and carbon surfaces with functionalised alkenes and alkynes. These functionalised surfaces have the disadvantage that they are not very stable. In addition, some methods of the prior art apply elevated temperatures (optionally in combination with UV-irradiation) which is detrimental to the homogeneity of the functionalisation and to the integrity of certain functionalised alkenes and alkynes.